Performance Analysis And Optimization Design Of Shaft Vertical Submersible Axial-Flow Pumping System

Shaft Vertical submersible axial-flow pumping system is generally composed of open sump,axial flow pump impeller,diffusion guide vane and wellbore outlet channel.Because of its simple structure,convenient maintenance and low investment,it has been used more and more in urban drainage and agricultural irrigation projects in recent years.However,the existing numerical simulation and model tests show that the head and efficiency of vertical submersible axial-flow pumping system are low.Therefore,it is of great significance to optimize the design of this pumping system to improve its hydraulic performance and reduce energy consumption.Based on the structure size of common vertical submersible axial-flow pump device,the basic vertical submersible axial-flow pump device is established.The commercial CFD software CFX is used to simulate the basic vertical submersible axial-flow pumping system,and the internal flow characteristics and hydraulic performance under different flow rates are analyzed.It is found that the hydraulic performance of the basic vertical submersible axial flow pump is poor,among which the open sump and impeller of the axial flow pump have better performance,while the hydraulic losses of the diffusive guide vane and the wellbore outlet channel are larger.There is a large range of recirculation area in the diffusive guide vane body under different flow rates,which makes the residual circulation at the outlet of the guide vane body larger.The water flow in the wellbore outflow channel has obvious back flow between the wellbore and the outlet pipe and forms a large range of vortices at the inlet of the outlet pipe.The area of the recirculation vortices increases with the increase of flow rate.The orthogonal experimental design was carried out for the first width of hub L1,the second width of hub L2,the distance d between guide vanes and the width L34 of flange in diffusive guide vane.It is found that the lift and efficiency of the pump device first increase and then decrease with the rise of L1;with the rise of L2 and L3,the lift and efficiency also show a trend of first increase and then decrease,but the overall change is not significant;with the gradual increase of d,the lift efficiency decreases.Through the analysis of k value,the factors affecting the efficiency of pump head are L1>L2>L3>d,and the optimal combination scheme is obtained by the comprehensive frequency method.The lift and efficiency of the scheme are 3.76 m and 74.6%respectively under the design conditions.Compared with the basic vertical submersible axial flow pump,the lift efficiency of the scheme is increased by 8%under the design flow rate,and the optimization effect is obvious.Orthogonal experimental design was carried out for four geometric parameters of shaft outlet pipe,such as length of rotation angle A,radius R of outlet pipe,camber angle of motor cap 0 and distance L between motor well and outlet pipe center line.It is found that with the gradual increase of A,the lift and efficiency of vertical submersible axial flow pump device show the trend of first rising and then decreasing;the lift and efficiency of pump device gradually increase with the increase of R and the rate of increase gradually decreases;with the increase of 0,the hydraulic performance of pump device first rises and then remains unchanged;and with the rise of L,the lift efficiency gradually rises.The factors affecting the lift efficiency of pumping devices are arranged in the order of R>L>0>A,considering that the project investment should not be too large.Through numerical simulation,the head efficiency of the optimal combination scheme under the designed flow rate is 3.94 m and 78.85%respectively,and the optimization effect is obvious.The steady and unsteady computations of the basic scheme and the final optimization scheme are carried out under different flow rates,and the comparative analysis is made.The results show that the internal flow pattern of the optimized diffusive guide vane is better than that of the basic scheme.The hydraulic loss of the guide vane is reduced by 26.5%under the designed flow rate.The flow pattern of the optimized wellbore outflow channel is better than that of the basic scheme.The backflow area in the inlet of the outlet pipe is smaller,and the hydraulic loss is 43.1%smaller than that of the basic scheme.Under different flow rates,the pressure fluctuation and pressure fluctuation intensity of each sampling point in the diffusion guide vane body of the optimized scheme are less than those of the basic scheme.Generally speaking,the flow characteristics,hydraulic performance and pressure fluctuation characteristics of the optimized scheme are better than those of the basic scheme.For the overall structure size of common vertical submersible axial-flow pump devices,it is recommended that(?)1 and(?)2 be maintained between 10.43(?)to 18.22 and 24.8(?)to 32.02(?)degrees,and that the overall height and radius of the wellbore outlet pipe be increased as much as possible within the scope of the project scale,and supplementary materials be added at the corner between the wellbore and the outlet pipe.